Composite member and method for producing composite member

ABSTRACT

A composite member includes a metal shaft member, and a fit member having an insertion hole and secured onto the shaft member inserted in the insertion hole. The shaft member includes a receiving portion contacting a first end surface of the fit member, a first radially enlarged portion adjacent to the receiving portion in an axial direction and tightly contacting an inner peripheral surface of the insertion hole, and a second radially enlarged portion adjacent to the first radially enlarged portion in the axial direction and tightly contacting a second end surface of the fit member opposite to the first end surface. The first and second radially enlarged portions are formed by applying a compressive load in the axial direction to the shaft member and an alternating load in a direction intersecting the axial direction to a portion of the shaft member inserted in the insertion hole.

TECHNICAL FIELD

The present invention relates to a composite member and a method for producing the composite member.

BACKGROUND ART

A related art rotating member includes a shaft member made of a metal and a fit member having an insertion hole in which the shaft member is fitted. The fit member is secured onto the shaft member by placing a portion of the shaft member inside the insertion hole and radially enlarging the portion of the shaft member so that the portion of the shaft member firmly contacts an inner peripheral surface of the insertion hole (see, e.g., JP2012-61520A).

When a rotating member of a similar profile is made of a single piece, stress is concentrated at a boundary between a portion corresponding to the shaft member and a portion corresponding to the fit member. However, with the rotating member having a two-piece structure, i.e., the shaft member and the fit member, such a concentration of stress is suppressed. Further, in a case where specifications of hardness are different between the shaft member and the fit member, the shaft member and the fit member can be individually quenched in accordance with their specifications, whereby the production cost can be reduced.

The fit member of the related art rotating member also has grooves formed on the inner peripheral surface of the insertion hole of the fit member in advance, so that the portion of the shaft member enters the grooves when being enlarged inside the insertion hole, whereby the strength at which the fit member is secured onto the shaft member is improved.

The enlarging of the shaft member is caused by plastic deformation of the shaft member. Thus, it is difficult to enlarge the portion of the shaft member to be fitted in the fit member uniformly along its entire circumference.

A variation in the enlargement of the shaft member may cause a locally insufficient contact between the shaft member and the inner peripheral surface of the insertion hole, and may lower the strength at which the fit member is secured onto the shaft member. To suppress the variation in the contact condition between the shaft member and the inner peripheral surface of the insertion hole, extremely high accuracy is required in fitting the shaft member in the insertion hole, which may require cutting of the outer diameter of the portion of the shaft member to be fitted into the insertion hole, and may lower the production efficiency.

The related art rotating member has the grooves on the inner peripheral surface of the insertion hole so that the portion of the shaft member is caught in the grooves to improve the strength at which the fit member is secured onto the shaft member. However, with the fit member being produced by, for example, forging, it is necessary to separately perform cutting to form the grooves on the inner peripheral surface of the insertion hole, which may again lower the production efficiency.

SUMMARY OF INVENTION

Illustrative aspects of the present invention provide a composite member having a fit member secured onto a shaft member by radially enlarging the shaft member inserted inside an insertion hole of the fit member, with improved fitting strength and higher production efficiency.

According to an illustrative aspect of the present invention, a composite member includes a shaft member made of a metal, and a fit member having an insertion hole, the fit member being secured onto the shaft member inserted in the insertion hole. The shaft member includes a receiving portion contacting a first end surface of the fit member, a first radially enlarged portion tightly contacting an inner peripheral surface of the insertion hole, the first radially enlarged portion being disposed adjacent to the receiving portion in an axial direction of the shaft member, and a second radially enlarged portion tightly contacting a second end surface of the fit member, the second end surface being opposite to the first end surface, and the second radially enlarged portion being disposed adjacent to the first radially enlarged portion in the axial direction.

According to another illustrative aspect of the present invention, a method for producing the composite member is provided. The method includes inserting a shaft member made of a metal into an insertion hole of a fit member such that a first end surface of the fit member contacts a receiving portion formed on the shaft member, and radially enlarging an inserted portion of the shaft member inserted in the insertion hole by applying a compressive load in an axial direction to the shaft member and an alternating load in a direction intersecting the axial direction to the inserted portion of the shaft member, thereby forming a first radially enlarged portion tightly contacting an inner peripheral surface of the insertion hole and a second radially enlarged portion tightly contacting a second end surface of the fit member, to secure the fit member onto the shaft member.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a shaft member and a fit member of an example of a composite member according to an embodiment of the present invention.

FIG. 2 is a plan view of the fit member.

FIG. 3 is a cross-sectional view of the composite member in which the shaft member is radially enlarged so that the fit member is secured onto the shaft member.

FIG. 4 is a schematic diagram illustrating an example of an apparatus for producing the composite member.

FIG. 5A is a schematic diagram illustrating an enlarging process using the apparatus of FIG. 4.

FIG. 5B is another schematic diagram illustrating the enlarging process.

FIG. 5C is another schematic diagram illustrating the enlarging process.

FIG. 5D is another schematic diagram illustrating the enlarging process.

FIG. 6 is a schematic diagram illustrating another example of a process for enlarging the shaft member.

FIG. 7 is a schematic diagram illustrating another example of a process for enlarging the shaft member.

FIG. 8 is a schematic diagram illustrating another example of a process for enlarging the shaft member.

FIG. 9 is a schematic diagram illustrating another example of a process for enlarging the shaft member.

DESCRIPTION OF EMBODIMENTS

FIGS. 1 and 2 illustrate a composite member 1 according to an embodiment of the present invention.

The composite member 1 includes a shaft member 2 and a fit member 3. The composite member 1 is, for example, a component of a continuously variable transmission (CVT) provided in a power transmission system of a vehicle, in which case the shaft member 2 corresponds to a pulley shaft and the fit member 3 corresponds to a pulley.

The shaft member 2 includes a small diameter portion 10 extending from one end in the axial direction, and a large diameter portion 11 provided adjacent, in the axial direction, to the small diameter portion 10. The shaft member 2 is made of a plastically deformable metal material such as a steel material, and is produced by, for example, forging. Although the shaft member 2 is made of a solid material in the illustrated example, it may be made of a hollow material.

The fit member 3 is a disc-shaped member, and has an insertion hole 12 in the center. A first end surface 13 a of the fit member 3 on one side is a substantially conical face surface, and a CVT belt is caught on this face surface. A second end surface 13 b of the fit member 3 or the other side is provided with a plurality of recesses 14 formed at intervals around the outer circumference of the insertion hole 12. An opening portion 16 of the insertion hole 12 on a side of the second end surface 13 b is gradually widened toward the second end surface 13 b. The fit member 3 is also made of a metal material such as a steel material, and is produced by, for example, the forging.

The small diameter portion 10 of the shaft member 2 is inserted through the insertion hole 12 of the fit member 3, to attach the fit member 3 onto the shaft member 2. A radially inner portion of the first end surface 13 a of the fit member 3 is caused to contact a step portion 15 between the small diameter portion 10 and the large diameter portion 11 of the shaft member 2, such that the fit member 3 is positioned with respect to the shaft member 2.

FIG. 3 illustrates a state where the shaft member 2 is radially enlarged to secure the fit member 3 onto the shaft member 2.

The small diameter portion (inserted portion) 10 of the shaft member 2 inserted into the insertion hole 12 of the fit member 3 is radially enlarged such that the shaft member 2 has a first radially enlarged portion 17 tightly contacting an inner peripheral surface of the insertion hole 12 and a second radially enlarged portion 18 tightly contacting the second end surface 13 b of the fit member 3. The small diameter portion 10 is radially enlarged by applying a compressive load in the axial direction to the shaft member 2 and by applying an alternating load in a direction intersecting the axial direction to the small diameter portion 10.

The first radially enlarged portion 17 of the shaft member 2 is in firm contact with the inner peripheral surface of the insertion hole 12, and the fit member 3 is sandwiched, in the axial direction, between the step portion (receiving portion) 15 contacting the first end surface 13 a of the fit member 3 and the second radially enlarged portion 18 tightly contacting the second end surface 13 b of the fit member 3, whereby the fit member 3 is secured onto the shaft member 2.

The shaft member 2 and the fit member 3, as the CVT component, are typically heat-treated by quenching or the like. For example, the fit member 3 around which the CVT belt is provided is quenched in advance by carburizing through, for example, a furnace heating, whereas the shaft member 2 is quenched after securing the fit member 3 onto the shaft member by, for example, induction heating that does not involve a carburizing treatment. In this manner, in the composite member 1 including the two members of the shaft member 2 and the fit member 3, the quenching can be individually performed in accordance with specifications of the shaft member 2 and the fit member 3, which can decrease the production cost.

The strength at which the fit member 3 is secured onto the shaft member 2 is improved not only by the first radially enlarged portion 17 of the shaft member 2 tightly contacting the inner peripheral surface of the insertion hole 12 but also by sandwiching the fit member 3 in the axial direction between the step portion 15 and the second radially enlarged portion 18 of the shaft member 2. In this manner, even if there is small variation in the contact between the first radially enlarged portion 17 of the shaft member 2 and the inner peripheral surface of the insertion hole 12 of the fit member 3, the fixing strength of the fit member 3 can be sufficiently attained. Further, since the fit member 3 is sandwiched in the axial direction between the step portion 15 and the second radially enlarged portion 18 of the shaft member 2 so as to attain the sufficient fixing strength of the fit member 3, accuracy required in fitting the small diameter portion 10 in the insertion hole 12 can be lowered, for example, to accuracy in the outer diameter of the small diameter portion 10 obtained by the forging, which can increase the production efficiency.

Due to the flow of a material of the shaft member 2 caused during the formation of the second radially enlarged portion 18, the second radially enlarged portion 18 is caught in the recesses 14 on the second end surface 13 b of the fit member 3, and thus, the strength at which the fit member 3 is secured to the shaft member 2 is further improved. In addition, the recesses 14 can be formed on the second end surface 13 b of the fit member 3 as part of the production of the fit member 3 by the forging, which can increase the production efficiency. Preferably, the recesses 14 are formed to extend in a radial direction from the inner peripheral surface of the insertion hole 12 of the fit member 3. Thus, the material of the shaft member 2 flown toward an outer diameter side during the formation of the second radially enlarged portion 18 can easily enter the recesses 14.

Instead of the recesses 14, projections may be formed on the second end surface 13 b of the fit member 3. With the projections on the second end surface 13 b of the fit member 3 engaging with the second radially enlarged portion 18 of the shaft member 2, the strength at which the fit member 3 is secured onto the shaft member 2 is improved, as in the case where the second radially enlarged portion 18 is caught in the recesses 14.

FIG. 4 illustrates an example of an apparatus 20 for producing the composite member 1.

The apparatus 20 includes a pair of holders 21, 22 disposed on a reference line A, a compressive load generator 23 applying a compressive load in the axial direction to the shaft member 2, and an alternating load generator 24 applying, to the shaft member 2, an alternating load in the direction intersecting the axial direction of the shaft member 2.

The holder 21 holds an end of the shaft member 2 on the side of the large diameter portion 1, and the holder 22 holds the other end of the shaft member 2 on the side of the small diameter portion 10. A holding projection 25 is provided on the bottom of the holder 22, and a fit recess 26 to be fit in the holding projection 25 is formed on the end of the shaft member 2 on the side of the small diameter portion 10 held by the holder 22. When the holding projection 25 is fit in the fit recess 26, the end of the shaft member 2 on the side of the small diameter portion 10 is held by the holder 22, and a gap is provided between an inner peripheral surface of the holder 22 and an outer peripheral surface of the small diameter portion 10.

With the small diameter portion 10 of the shaft member 2 inserted through the insertion hole 12 of the fit member 3, the shaft member 2 is held in the axial direction between the holders 21, 22 and is aligned on the reference line A. With the radially inner portion of the first end surface 13 a of the fit member 3 contacting the step portion 15 of the shaft member 2 such that the fit member 3 is positioned with respect to the shaft member 2, the fit member 3 is also held on the reference line A coaxially with the large diameter portion 11 by the holder 21 holding the end of the shaft member 2 on the side of the large diameter portion 11.

The compressive load generator 23 causes the holder 21, which holds the end of the shaft member 2 on the side of the large diameter portion 11, to make translational movement along the reference line A, so as to apply the compressive load in the axial direction to the shaft member 2 through the holders 21, 22.

The alternating load generator 24 bends the small diameter portion 10 by inclining the holder 22, which holds the end of the shaft member 2 on the side of the small diameter portion 10, so as to make the rotational axis of the holder 22 oblique against the reference line A. Then, the alternating load generator 24 rotates the inclined holder 22 around the rotational axis so as to apply the alternating load in the direction intersecting the axial direction of the shaft member 2.

FIGS. 5A to 5D illustrate a process of enlarging the shaft member 2 using the apparatus 20.

As illustrated in FIG. 5A, the holder 21 is caused to make translational movement along the reference line A by the compressive load generator 23 (see FIG. 4), and thus, the compressive load in the axial direction is applied to the shaft member 2 held between the holders 21, 22. The holder 22 is inclined with respect to the reference line A and rotated by the alternating load generator 24 (see FIG. 4). The angle of the inclination of the holder 22 is set to an angle at which the bent of the shaft member 2 can be deformation within the elastic limit, and is typically about 2 degrees to 3 degrees.

As illustrated in FIG. 5B, the small diameter portion 10 of the shaft member 2 held between the holders 21, 22 is bent around a center O on the reference line A slightly shifted from the fit member 3 in the axial direction of the shaft member 2, and is rotated around the axis of the shaft member 2. In accordance with the rotation, the alternating load in the direction intersecting the axial direction of the shaft member 2 is applied to the small diameter portion 10 of the bent shaft member 2 in an inside portion and an outside portion thereof in the bending direction. The portion of the small diameter portion 10 on the inner side of the bending direction is expanded due to plastic flow, and as the shaft member 2 is rotated around the axis, the expansion caused by the plastic flow grows over the entire circumference, and thus, the small diameter portion 10 is radially enlarged.

As illustrated in FIG. 5C, due to the radial enlargement of the small diameter portion 10, the first radially enlarged portion 17 tightly contacting the inner peripheral surface of the insertion hole 12 of the fit member 3 is formed inside the insertion hole 12 of the fit member 3. Also on the outside the insertion hole 12 of the fit member 3, the small diameter portion 10 is radially enlarged to fill the gap provided between the inner peripheral surface of the holder 22 and the outer peripheral surface of the small diameter portion 10 and to fill a gap formed between the end surface of the holder 22 and the second end surface 13 b of the fit member 3, whereby the second radially enlarged portion 18 tightly contacting the second end surface 13 b of the fit member 3 is formed. Since the opening portion 16 (see FIG. 1) of the insertion hole 12 on the side of the second end surface 13 b is gradually widened, an excessive material of the small diameter portion 10 enlarged inside the insertion hole 12 flows toward the second end surface 13 b, and this accelerates the formation of the second radially enlarged portion 18.

As illustrated in FIG. 5D, after forming the first radially enlarged portion 17 and the second radially enlarged portion 18, the compression of the shaft member 2 is stopped, and the shaft member 2 is restored by causing the holder 22 inclined with respect to the reference line A to be aligned along the reference line A again. In this manner, the enlargement process of the shaft member 2 is completed, and the rotation of the shaft member 2 is stopped.

Then, the composite member 1 in which the fit member 3 is fixed on the shaft member 2 is removed from the holders 21, 22.

The process for enlarging the shaft member 2 is not limited to the example illustrated in FIGS. 5A to 5D. FIGS. 6 to 9 respectively illustrate other examples of a process for enlarging the shaft member 2.

In the example of FIG. 6, the alternating load is applied by bending the small diameter portion 10 of the shaft member 2 and rotating it around the axis in the same manner as in the example of FIGS. 5A to 5D. On the other hand, instead of inclining the holder 22 against the reference line A, the holder 22 is slid in a direction intersecting the reference line A for bending the small diameter portion 10.

In the example of FIG. 7, the end of the shaft member 2 on the side of the large diameter portion 11 is held in an unrotatable manner in a constrained state by the holder 21, and the other end of the shaft member 2 on the side of the small diameter portion 10 is rotatably held in an unconstrained state by the holder 22. Under these conditions, the end held by the holder 22 is caused to gyrate around the reference line A, so as to bend the shaft member 2 and apply the alternating load to the small diameter portion 10 of the shaft member 2.

In the example of FIG. 8, the alternating load is applied to the small diameter portion 10 of the shaft member 2 by reciprocatingly rotating, so as to cross over the reference line A, the holder 22 holding the end of the shaft member 2 on the side of the small diameter portion 10.

In the example of FIG. 9, the alternating load is applied to the small diameter portion 10 of the shaft member 2 by applying bending or twisting vibration to the shaft member 2 by a vibration generator OSC.

While present invention has been described with reference to certain embodiments thereof, the scope of the present invention is not limited to the embodiments described above, and it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the scope of the present invention as defined by the appended claims. For example, the shaft member 2 and the fit member 3 may not be a pulley shaft and a pulley, and the fit member 3 may be a gear or the like.

This application is based on Japanese Patent Application No. 2015-207395 filed on Oct. 21, 2015, the entire content of which is incorporated herein by reference. 

1. A composite member comprising: a shaft member made of a metal; and a fit member having an insertion hole, the fit member being secured onto the shaft member inserted in the insertion hole, wherein the shaft member comprises: a receiving portion contacting a first end surface of the fit member; a first radially enlarged portion tightly contacting an inner peripheral surface of the insertion hole, the first radially enlarged portion being disposed adjacent to the receiving portion in an axial direction of the shaft member; and a second radially enlarged portion tightly contacting a second end surface of the fit member, the second end surface being opposite to the first end surface, and the second radially enlarged portion being disposed adjacent to the first radially enlarged portion in the axial direction.
 2. The composite member according to claim 1, wherein the fit member comprises at least one recess or projection on the second end surface, and wherein the second radially enlarged portion is engaged with the recess or the projection is engaged with the second radially enlarged portion.
 3. The composite member according to claim 1, wherein an opening portion of the insertion hole of the fit member on a side of the second end surface is gradually widened toward the second end surface.
 4. A method for producing a composite member, the method comprising: inserting a shaft member made of a metal into an insertion hole of a fit member such that a first end surface of the fit member contacts a receiving portion formed on the shaft member; and radially enlarging an inserted portion of the shaft member inserted in the insertion hole by applying a compressive load in an axial direction to the shaft member and an alternating load in a direction intersecting the axial direction to the inserted portion of the shaft member, thereby forming a first radially enlarged portion tightly contacting an inner peripheral surface of the insertion hole and a second radially enlarged portion tightly contacting a second end surface of the fit member, to secure the fit member onto the shaft member.
 5. The method according to claim 4, wherein at least one recess or projection is formed on the second end surface of the fit member, and the enlarging the inserted portion of the shaft member comprises causing the second radially enlarged portion to enter the at least one recess or causing the at least one projection to bite into the second radially enlarged portion.
 6. The method according to claim 4, wherein an opening portion of the insertion hole of the fit member on a side of the second end surface is gradually widened toward the second end surface, and the enlarging the inserted portion of the shaft member comprises causing an excessive material of the inserted portion enlarged inside the insertion hole to flow toward the second end surface.
 7. The composite member according to claim 2, wherein an opening portion of the insertion hole of the fit member on a side of the second end surface is gradually widened toward the second end surface.
 8. The method according to claim 5, wherein an opening portion of the insertion hole of the fit member on a side of the second end surface is gradually widened toward the second end surface, and the enlarging the inserted portion of the shaft member comprises causing an excessive material of the inserted portion enlarged inside the insertion hole to flow toward the second end surface. 